Caching occurs at three levels. One at the origin server level, one at the CDN edge server level, and the third at client browser level. All three layers of caching use expiration caching.
1. Origin Server caching (Scene7 Platform Server)
The Scene7 origin servers cache most of the requests on disk. Origin server caching is based on a catalog time stamp. With every publish job, a catalog file is updated and all cached requests that use the updated catalog file is refreshed automatically.
Origin server caching is based on the modifiers applied to the image. If the URL modifiers are moved around slightly, or if they use modifiers that the platform server ignores (such as sessionid), it retrieves the cached image.
If images are published from an SPS system, the expiration is set to ten hours by default.
2. CDN Edge Server caching
In general, the CDN caches all requests. But, there are some exceptions, the Scene7 viewers use to request updated content immediately.
Again, expiration caching is used to refresh the contents, unless otherwise the user manually clears it.
3. Client-side caching (browser caching):
Scene7 platform server also sends an expiration time in the image response. By default, SPS sets this value to ten hours. Therefore, a client browser doesn't request a new image for ten hours, unless the browser is set to validate images every time. The CDN can honor this ten hours TTL as well, but it can also be configured to overwrite it. You can look at your browser cache to find out which one of the files are cached and for how long. In Firefox, type about:cache in the address bar to view the cached items.